1. Field of the Invention
The present invention relates to electromagnetic interference (EMI) shielding and more particularly to a window wall for a shielded enclosure.
2. Description of the Prior Art
Shielded enclosures are used to attenuate interference from electromagnetic radiation, such as radio frequency radiation. Such enclosures may include a single shield of electrically conductive metal or multiple shields of electrically conductive metal and/or metal mesh entirely enclosing a shielded space. Where apertures are required in the shield for windows, doors, ventilation, power feedthrus and the like, it is important to maintain the integrity of the shielding.
Typical windows for shielded enclosures used in the past have included one or two fine wire mesh screens electrically connected to the shield or shields of the enclosure. One difficulty with screen windows is that they are not optically transparent. Even with extremely fine wire screens, visibility through the window is impaired. When two screens are employed, typically visual interference occurs in waves or patterns caused by a moire effect. U.S. Pat. No. 5,012,041, issued Apr. 30, 1991, and assigned to the present assignee, discloses a screened window including two wire screens having different mesh patterns arranged for substantially avoiding conventional optical interference.
While the screened window disclosed by the above-identified patent provides substantial improvements over the prior art arrangements, it is desirable to provide an improved window for larger openings or a window wall for a shielded enclosure that is easy to install and that effectively preserves the shielding integrity of the shielded enclosure.